The key objective of this study is to collect the first nationally representative data on prevalences and correlates of DSM-IV MDD from the recently completed National Comorbidity Survey Replication (NCS-R). The study design is a direct interview household survey of a probability household survey of adults ages 18 and over from the 48 contiguous United States. The total number of subjects in the study is 9090, representing a 79% response rate. The diagnostic interview was the WHO Composite International Diagnostic Interview (CIDI), developed to collect diagnostic criteria for the DSM-IV. Clinical re-interviews were carried out with the Structured Clinical Interview for DSM-IV (SCID) to validate CIDI diagnoses. The NCS research program consists of a series of surveys associated with the U.S. National Comorbidity Survey (NCS). The baseline NCS, fielded from the fall of 1990 to the spring of 1992, was the first nationally representative mental health survey in the U.S. to use a fully structured research diagnostic interview too assess the prevalences and correlates of DSM-III-R disorders. The baseline NCS respondents are being reinterviewed in 2001-02 (NCS-2) to study patterns and predictors of the course of mental and substance use disorders and to evaluate the effects of primary mental disorders in predicting the onset and course of secondary substance disorders. In conjunction with this, an NCS Replication survey (NCS-R) is being carried out in a new national sample of 10,000 respondents. The goals of NCS-R are to study trends in a wide range of variables assessed in the baseline NCS and to obtain more information about a number of topics either not covered in the baseline NCS or covered in less depth than we currently desire. A survey of 10,000 adolescents (NCS-A) is being carried out in parallel with the NCS-R and NCS-2 surveys. The goal of NCS-A is to produce nationally representative data on the prevalences and correlates of mental disorders among youth. NCS-R and NCS-A, finally, are being replicated in a number of countries around the world. Centralized cross-national analysis of these surveys is being carried out by the NCS data analysis team under the auspices of the World Health Organization World Mental Health Survey Initiative. During the past year, we have completed the primary analyses of the National Comorbidity Survey-Replication data. The results were presented in the June issue of the Archives of General Psychiatry. There are several major findings from these papers: First, as reported in earlier population-based studies, mental disorders begin in early life and are common and protracted. As suggested in the W.H.O. Burden of Disease study (15), mental illnesses are the chronic diseases of the young. Kessler et al find lifetime history of a mental disorder in 46.4 % of their sample and a 12-month prevalence of 26.2%, with half of all cases reporting onset by age 14 and three-quarters by age 24. Secondly, Kessler et al report that more than half of those diagnosed with a disorder in the previous 12 months were rated as ?serious? (22.3%) or ?moderate? (37.3%) rather than mild. Those rated as ?serious? (5.8% of the population) reported a mean of 88.3 days when they were unable to carry out their normal daily activities because of mental or substance abuse problems. Ratings of ?serious? were most common among bipolar disorder (83%), drug dependence (56.5%), obsessive-compulsive disorder (50.6%), oppositional-defiant disorder (49.6%), and mood disorders (45%). Corroborating the high rates of comorbidity described in earlier studies, 45% of the population met criteria for two or more disorders, with severity strongly related to comorbidity. Finally, mental health care in America is ailing. Over a 12-month period, 60% of those with a disorder (recall that 60% of these are serious or moderate) receive no treatment. While the survey can only crudely estimate adherence to evidence-based standards and adequacy of treatment, the sources of care are informative. Those with a mental or substance use disorder were more likely to receive help from a general medical professional (e.g. primary care physician or nurse) or a complementary-alternative source (e.g. internet support group) than a psychiatrist. Yet, quality of treatment is much higher in mental health specialty care (minimally adequate in 48.0% of specialty mental health vs. 12.8% of general medical and 13.1% for non-healthcare). We have also analyzed data and completed manuscripts on the following topics: migraine and other headaches, the spectrum of bipolar disorder, sex differences in mood disorders, the impact of mental and physical disorders on work disability, and comorbidity between sleep and mood disorders. During the next year, we plan to complete these manuscripts and continue to analyze the data. We will also prepare the data for public access within the next 6 months.